The present invention relates to a method for detecting organic contamination in a process equipment of manufacturing integrated circuits, more specifically, to a method for detecting organic contamination in a process equipment of manufacturing integrated circuits by using the fabrication of hemispherical polysilicon grains in the integrated circuits.
During the fabrication of integrated circuits, several kinds of contamination contaminates silicon wafers or the integrated circuits on the silicon wafers. The kinds of contamination include conductive-dopant contamination, metal impurity, native oxide contamination and organic impurity contamination. In general, these kinds of contamination seriously influents the yield for manufacturing integrated circuits on wafers. Thus, how to detect the contamination on silicon wafers or to clean the contamination on wafers becomes a very important issue. In the following descriptions, the method to detect these kinds of contamination will be explained.
At first, conductive-dopant contamination often occurs, as the ion implantation process is performed to dope silicon wafers, which integrated circuits are formed thereon, during the fabrication of the integrated circuits. The conductive dopant will be a contamination source of silicon wafers. Generally, a method to detect the conductive-dopant impurity is performed by using X-ray detecting technique or measuring resistive constant to determine whether the silicon wafers are suffered from the conductive-dopant contamination. Furthermore, metal-impurity contamination can be detected by specified detecting technique and it still can be effectively found.
About the contamination source of native oxide, conventional techniques can be effectively detected. The method for removing the native-oxide contamination is to clean the surface of silicon wafers by using HF solution that can easily remove the native oxide layer on the silicon wafers.
Special equipment is needed for detecting organic contamination on silicon wafers. Nevertheless, the special equipment can not be located in a clean room. If silicon wafers would be detected whether organic impurity contaminates the surface of the silicon wafers, the wafers must be moved out of the cleaning room, which the integrated circuits on the silicon wafers are fabricated therein, for the measurement of organic contamination. Moreover, the special equipment can not rapidly detect the organic contamination on silicon wafers for the large throughput of integrated circuits. Additionally, as silicon wafers are moved out of cleaning rooms, the silicon wafers will suffered from organic contamination. It is hard to determine whether organic contamination is formed on the surface of silicon wafers, in other words, organic contamination on silicon wafers can not be precisely measured.
During the fabrication of integrated circuits in cleaning rooms, silicon wafers, which the integrated circuits are formed thereon, are put into wafer cassettes for the transferring in batch. Before silicon wafers are loaded into wafer cassettes, the cassettes are cleaned by using acetone solution to remove the contamination on wafer cassettes. Nevertheless, acetone solution is indicated as organic material. Thus, after the cleaning process by using acetone solution, the wafer cassettes are cleaned by using dilute-ion (DI) water for removing the acetone residue on the cassettes. But, the above cleaning process can not completely remove the acetone residue on the cassettes. Consequently, organic contamination on the cassettes is residual after the acetone cleaning process. As silicon wafers are loaded into the wafer cassettes, the silicon wafers are contaminated by the acetone residue on the cassettes and the acetone residue is indicated as a main source of organic contamination.
According to the above discussion, there is no effective and rapid method to detect organic contamination on silicon wafers in the technique of fabricating integrated circuits. The present organic detecting technique is performed out of a cleaning room and can not in-situ detect organic contamination on silicon wafers. Therefore, an in-situ organic contamination detecting method in a cleaning room is needed for in-situ improving the process environment of integrated circuits.
The present invention provides a method for detecting organic contamination in a process environment by using the deposition of hemispherical polysilicon grains. A semiconductor substrate is provided and an amorphous silicon layer is deposited on the substrate. Subsequently, the amorphous silicon layer is transformed into a hemispherical-grain polysilicon layer on the substrate. The grain size of the hemispherical-grain polysilicon layer is measured to determine whether the organic contamination is residual on the substrate.
The present invention provides a preferred embodiment disclosing that the grain size of the hemispherical-grain polysilicon layer is measured, as the grain size is between about 0.2 to 0.4 micrometers, the organic contamination is residual on the semiconductor substrate; as the grain size is between about 0.5 to 0.8 micrometers, the organic contamination is not residual on the semiconductor substrate.
The present invention provides a preferred embodiment providing a cleaning process performed on the semiconductor substrate to remove the organic contamination on the semiconductor substrate before the hemispherical-grain polysilicon layer is formed.
The present invention provides a preferred embodiment disclosing the cleaning process cleans the semiconductor substrate by using acetone solution.
The present invention provides a preferred embodiment disclosing organic contamination comprises the contamination of acetone solution.
In a preferred embodiment of the present invention, the organic contamination has influence with the growth of the hemispherical-grain polysilicon layer, so that the grain size of the hemispherical-grain polysilicon layer is smaller than 0.4 micrometers.
In a preferred embodiment of the present invention, the semiconductor substrate is suffered from the organic contamination, which is indicated as the process environment is suffered from the organic contamination.